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Go Back   SailNet Community > General Interest Forums > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #31  
Old 02-10-2010
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WM: you're close...
Well if I am close I'll just go all the way to the South Pole then.
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  #32  
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Correct

Next:


It is almost noon and the moon is just beginning to rise. What phase is it?
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  #33  
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Correct

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It is almost noon and the moon is just beginning to rise. What phase is it?
Hmm, that would be a waning half moon ?

Yes, it would be a half moon with the light side facing the Sun's direction, I'm wrong, that would be a waxing half moon, after new and before full.

That right ?
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  #34  
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Well, the light side of the moon is always facing the sun for obvious reasons, but yes, you're right

Technically there's no such thing as a "half moon". The name of the phase is the third quarter.

I like to use the moon to help with navigation in the woods. You can usually deduce whether it's waxing or waning by time of day or night, and then you can roughly determine east and west.

Next quiz question:

I am using an artificial horizon to take sights with a sextant. What dip correction should I apply?
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Well, the light side of the moon is always facing the sun for obvious reasons, but yes, you're right
I was thinking aloud when I wrote that, trying to figure out if it was waxing or waning, I had my head tilted sideways and was thinking about the light being on the right side when I wrote that the light would be on the Sun side.

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Technically there's no such thing as a "half moon". The name of the phase is the third quarter.
Here there is a half moon, we don't care what scientists call it.

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Next quiz question:

I am using an artificial horizon to take sights with a sextant. What dip correction should I apply?
I don't know the answer to that one.
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The name of the phase is the third quarter.
I wonder about this, you said the Moon was rising at noon, right ? That phase seems like it would be called the first quarter, not the third, because it would be the first quarter moon after the new moon, waxing, not the last quarter before the new moon which is waning and setting at noon.
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I wonder about this, you said the Moon was rising at noon, right ? That phase seems like it would be called the first quarter, not the third, because it would be the first quarter moon after the new moon, waxing, not the last quarter before the new moon which is waning and setting at noon.
Ah, crap, you're right. If the moon is rising at noon, the sublunar point must be east of (CCW from above) the subsolar point, not west as I had in the picture in my head. Thanks
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If you spread your thumb from the rest of your fingers making an "L" shape, and you reach out into the sky with the tip of your thumb covering an object in the sky, approximately how many degrees away will the tip of your index finger be ?
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13 degrees... but I cheated and used a sextant
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I am using an artificial horizon to take sights with a sextant. What dip correction should I apply?
Dip correction is applied because your eye isn't right on the surface of the Earth; the higher you get, the farther you can see and so the lower the horizon appears, adding a few minutes of arc to your measurements.

An artificial horizon is a reflecting surface parallel to the horizon; you line up the object being sighted with its own reflection, so you're never looking at the horizon, so there is no dip correction.

My next question: suppose late tonight, Feb 14, the bright star Sirius passes directly overhead at 0800 GMT. What is my latitude and longitude?

p.s. this online nautical almanac might help
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